Stabilized chlorine-containing resin composition and process for preparing the stabilizer therefor

ABSTRACT

A METHOD OF PREPARING COPOLYMERS OF METAL SALTS OF UNSATURATED CARBOXYLIC ACIDS, SUITABLE FOR USE AS A STABILIZER FOR CHLORINE-CONTAINING RESINS, SUCH AS POLYVINYL CHLORIDE, BY MEANS OF PRECIPITATION COPOLYMERIZATION IN AN ALCOHO; SOLUTION CONTAINING WATER. A STABILIZED COMPOSITION COMPRISING A MIXTURE OF SAID COPOLYMERS OF METAL SALTS OF UNSAUTRATED CARBOXYLIC ACIDS AND CHLORINE-CONTAINING RESIN.

United States Patent m 3,803,267 STABILIZED CHLORINE-CONTAINING RESINCOMPOSITION AND PROCESS FOR PREPAR- ING THE STABILIZER THEREFOR KenshiKuwahara, Shigetada Sonoda, and Masahito Ishii, Tokyo, Japan, assiguorsto Mitsui Mining & Smelting Co., Ltd., Tokyo, Japan No Drawing.Application Dec. 4, 1969, Ser. No. 882,280,

now Patent No. 3,705,137, which is a continuation-inpart of abandonedapplication Ser. No. 612,808, Jan. 31, 1967. Divided and thisapplication July 11, 1972, Ser. No. 270,576

Int. Cl. C08f 15/08, 29/14 US. Cl. 260-890 4 Claims ABSTRACT OF THEDISCLOSURE A method of preparing copolymers of metal salts ofunsaturated carboxylic acids suitable for use as a stabilizer forchlorine-containing resins, such as polyvinyl chloride, by means ofprecipitation copolymerization in an alcohol solution containing water.A stabilized composition comprising a mixture of said copolymers ofmetal salts of unsaturated carboxylic acids and chlorine-containingresin.

This is a division of application Ser. No. 882,280, filed Dec. 4, 1969,now US. Pat. No. 3,705,137, which in turn is a continuation-in-part ofcopending application Ser. No. 612,808, filed Jan. 31, 1967, nowabandoned.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to a method of preparing polyvalent copolymers of two or moremonomers consisting of (l) at least one metal salt of an unsaturatedacid selected from the group consisting of the zinc, lead, cadmium,aluminum and alkaline earth metal salts of acrylic acid, rnethacrylicacid and crotonic acid and (2) at least one polymerizable vinyl monomerselected from the group consisting of acrylic esters, rnethacrylicesters, vinyl ethers, styrene, acrylonitrile, vinyl chloride andvinylidene chloride, and also relates to a composition obtained byadding the foregoing copolymer to a chlorine-containing resin forstabilization purposes.

Description of the prior art In the synthetic resin industry, it hashitherto been common to mix stabilizers with resin materials which areto be made into film and other processed goods. The addition of thestabilizer to the resin reduces or prevents the deterioration of theresin composition due to expo sure to heat and/or light during and afterits processing. The resin composition thereafter is made into moldedgoods suitable for various purposes.

The stabilizers in general use for making such stabilized resincompositions include the metal salts of higher fatty acids such asstearic acid, metal salts of organic acids such as naphthenic acid,octyl acid, acetacetyl acid, etc., and organic tin compounds. However,combinations of two or three or more of these stabilizers are usuallyemployed and even the combined use of many stabilizers in the prior arthas not always sufficed to provide an adequate stabilization property.

Especially, when a vinyl chloride resin composition is to be used forpackaging food, the stabilizer employed therewith must be nontoxic and,accordingly, it has been customary to employ stabilizer approved by theFDA, such as calcium-zinc mixed soap, epoxidized soybean oil and octyltin compound. However, the former two stabilizers have poor thermalstability while the latter stabilizer can be used in only limitedamounts. Thus, it has not been possible to provide a vinyl chlorideresin composition having the desired thermal stability.

SUMMARY OF THE INVENTION The stabilizer to be employed withchlorine-containing resins according to the present invention is apowder form copolymer which is superior to conventional stabilizers inefiiciency. The stabilizer consists essentially of a copolymer of:

(1) At least one metal salt selected from the group consisting of thezinc, lead, cadmium, calcium, magnesium, barium and aluminum salts of anacid selected from the group consisting of acrylic acid, methacrylicacid and crotonic acid; and

' (2) At least one polymerizable vinyl monomer selected from the groupconsisting of alkyl acrylate esters whose alkyl group has 1 to 18 carbonatoms, alkyl methacrylate esters whose alkyl group has 1 to 18 carbonatoms, styrene, acrylonitrile, alkyl vinyl ethers whose alkyl group has1 to 18 carbon atoms, vinyl chloride and vinylidene chloride.

The copolymer according to the present invention is adapted for use as astabilizer for chlorine-containing resins and it possesses numerousadvantageous characteristics, including:

(a) Molded products made of a chlorine-containing resin and saidcopolymer are colorless and transparent except when a lead-containingcopolymer is used;

(b) The copolymers containing the calcium, magnesium, aluminum or zincsalts of unsaturated carboxylic acids result in less metal etlluence ascompared with metallic soaps of the same metals as used in the prior artand, accordingly, the stabilizers according to the present invention areless toxic;

(c) When compared in terms of the same metals, the copolymer stabilizeraccording to the present invention provides greatly superior thermalstability and weatherproof property (light resistance) as compared tothe metallic soaps or metal salts of the prior art;

(d) The copolymer stabilizer has an excellent mutual solubility withchlorine-containing resins; and

(e) It prevents plate-out during the processing of a chlorine-containingresin composition.

Now, the method of preparing the copolymers for use as the stabilizeraccording to the present invention will be described in the following.

To begin with, inasmuch as the present copolymers are intended for useas a stabilizer for chlorine-containing resins, the copolymers to beformed should be easily soluble in or uniformly dispersible intochlorine-containing resins. In addition, in order to meet suchrequirements as satisfactory thermal stability as referred to in theforegoing (c) and processing efiiciency as referred to in the foregoing(e), they should not contain any substantial amount of unreactedmonomers.

The method according to the present invention provides a procedure forpreparing the copolymers in the form of an extra fine powder (with amean grain size of about 0.05- 6,u.) suitable for use as a stabilizer.The method is characterized by the steps of: causing at least one memberselected from the group consisting of the zinc, lead, cadmium, aluminumand alkaline earth metal salts of an acid selected from the groupconsisting of acrylic acid, methacrylic acid and crotonic acid and atleast one member selected from the group consisting of acrylic esters,methacrylic esters, alkyl vinyl ethers, styrene, vinyl esters, acryl0-nitrile, vinyl chloride and vinylidene chloride to mutually dissolve inan aqueous solution containing at least one member selected from thegroup consisting of methyl alcohol, ethyl alcohol, propyl alcohols andisobutyl alcohol and mixtures thereof; and causing the resultantsolution to be copolymerized in the presence of a radical polymerizationinitiator, such as a peroxide like benzoyl peroxide, an azo compoundlike azobisisobutyronitrile, or potassium persulfate and sodium hydrogensulfite.

The compounding (weight) ratio of the salts of unsaturated carboxylicacids the first essential component, and the vinyl monomers, the secondessential component, is a very important factor in producing an extrafine powder capable of serving the foregoing purpose. When the weightratio of the metal salt of unsaturated carboxylic acid to the totalweight of monomers included in the reaction system is excessively small,the resultant copolymer takes the form of a clot (a mass of more thanseveral mm. in size) or the form of a sticky gel, and it is difiicult toobtain the desired end product in the form of extra fine powder. If thereaction product takes the form of a clot, it becomes very difficult toremove completely the solvent and the unreacted monomer therefrom. As aresult, when a clot-form copolymer is employed as a stabilizer, itsstabilizing effect on the resin composition is remarkably reduced due toeven a very small amount of unreacted monomer remaining therein, and,not only that, it must be pulverized because of its clot form and, evenif it is somehow pulverized, its dispersibility and mutual solubility inthe resin is unsatisfactory.

n the other hand, when the weight ratio of the salts of unsaturatedcarboxylic acids to the total weight of monomers included in thereaction system is extremely large, the efliciency of the resultantcopolymer is reduced so that it becomes similar to that of a polymer ofthe salts of unsaturated carboxylic acids alone. As a result, when it isemployed as a stabilizer, its thermal stability effect and mutualsolubility with the chlorine-containing resin is reduced.

In view of the foregoing, the weight ratio of the salts of unsaturatedcarboxylic acids contained in the reaction system is between about 8.0percent by equivalent and about 75 percent by equivalent based on thetotal weight of the monomers in said reaction system.

The water content of the aqueous alcohol solution to be employed as thereaction solvent also constitutes a very important factor. When thewater content of the aqueous alcohol solution is large, not only is thesolubility of the vinyl monomer, the second essential component, reducedso that the solution become divided into two phases, but also theresultant copolymer takes the form of a clot, not the form of a powder.On the other hand, when the water content is excessively small, thesolubility of the salts of unsaturated carboxylic acids decreases.Therefore, the water concentration in the aqueous alcohol solution foruse as a solvent in the reaction system must be between about weightpercent and about 5 0 weight percent.

The polymerizing method according to the present invention is aprecipitation copolymerization. To be more precise, the aforesaidmonomers are mutually dissolved in a reaction solvent consisting of anaqueous alcohol solution, and then a polymerization initiator is addedto the thus obtained solution, thereby giving rise to the formation of acopolymer of an unsaturated carboxylic acid saltvinyl monomer, whichcopolymer is insoluble in said solvent. Either an open type receptacleequipped with a reflux condenser or a pressure autoclave can be used asthe reaction vessel. Alternatively, continuous polymerization can beelfected by passing the foregoing mixture through a heated pipe.Agitation of the mixture is not always required, but it is preferablefor the sake of obtaining a uniform copolymer.

In the present invention, the polymerization conditions constitute avery important factor for obtaining a uniform powder having a grain sizeof less than several microns.

The rate of polymerization of metal salts of unsaturated carboxylicacids (strictly speaking, the monomer reactive ratio of salts ofunsaturated carboxylic acids) is extremely high as compared with that ofvinyl monomers, the second component. (In general, the monomer reactiveratio r for metal salts of unsaturated carboxylic acids is in the rangeof 5-20, while the monomer reactive ratio r for vinyl monomers is in theHinge of 0.0-0.5.) Therefore,

according to the batch method of polymerization, tse composition ratioof unreacted monomers in the reaction system changes with the progressof the polymerization reaction. In other words, as the polymerizationreaction progresses, the weight ratio of salts of unsaturated carboxylicacids within the monomers in the reaction system decreases until itbecomes less than 8.0 percent by equivalent. If the polymerizationreaction is allowed to continue in this condition, there will be formeda clot-form copolymer in the later stages of the polymerization reactionand, consequently, the thus formed clot-form copolymer product will bemixed into the previously formed powder-form copolymer. Such a copolymermixture has a reduced efficiency as a stabilizer, so that it isnecessary either to discontinue the polymerization reaction before theaforesaid content ratio of the metal salts of unsaturated carboxylicacids becomes about 8.0 percent by equivalent or to add extra metal saltmonomers of unsaturated carboxylic acids from time to time as needed toassure that the content is never less than 8.0 percent by equivalentwithin the reaction system. However, there is an exception to thisgeneral rule, namely, when there is used a higher alkyl vinyl ether(whose alkyl group contains 8-18 carbon atoms) as the vinyl monomerconstituting the second component of the copolymer. When a higher alkylvinyl ether is used, even when said ratio falls below the foregoingvalue, to wit, the amount of the salts of unsaturated carboxylic acidsbecomes less than 8 percent by equivalent, an extra line powder-formcopolymer can be formed and, when almost all of the salts of carboxylicacids are polymerized, the polymerization reaction in the reactionsystem ceases naturally.

In the batch method of polymerization, the maximum polymer yield, whenthe copolymer is to be obtained in the form of powder, is very closelyrelated with the composition of the monomers introduced, the reactiontemperature, the amount of polymerization initiator used and the lengthof the polymerization period. For instance, once the composition ofmonomers introduced, the reaction temperature and the polymerizationinitiator are determined, the polymerization period for realizing amaximum polymer yield of necessity becomes fixed. However, thepolymerization period depends on a number of variables so that it cannotbe described precisely.

The copolymer obtained under the foregoing conditions can be easily andcompletely separated from unreacted monomers by filtering it and washingit with an aqueous alcohol solution Further, by subjecting the thusseparated copolymer to vacuum drying, there is obtained an extra finepowder of low apparent specific gravity.

Next, there will be given a detailed explanation of the stabilizedcompositions consisting of a chlorine-containing resin with a copolymerstabilizer prepared as described a ove.

The term chlorine-containing polymer" as referred to in the presentdescription shall refer to the polymers enumerated below:

(a) Polyvinyl chloride (a straight polymer) '(b) Polyvinylidene chloride(a straight polymer) (c) Copolymer comprising vinyl chloride and/orvinylidene chloride, and at least one additional monomer selected fromthe group consisting of vinylidene chloride, ethylene, propylene,isobutylene, acrylonitrile, alkyl vinyl ether (whose alkyl groupcontains 1-18 carbon atoms), vinyl alkyl ester (whose alkyl groupcontains 1-18 carbon atoms), acrylic ester (wherein the alkyl group ofthe ester contains l-18 carbon atoms), methacrylic ester (wherein thealkyl group of the ester contains 1 to 18 carbon atoms), styrene, maleicanhydride, maleic ester (wherein the alkyl group of the ester contains 1to 18 carbon atoms) and vinyl chloride.

(d) A blended mixture consisting of (1) at least one m m e of the g ponsist g f p lymers of the foregoing types (a) through (c) and (2) atleast one member selected from the group consisting of styrene-butadienecopolymers, acrylonitrile-butadiene copolymers, acrylonitrile-styrenecopolymers, acrylonitrile-butadiene-styrene copolymers,methylmethacrylate butadiene styrene copolymers and ethylene-vinylacetate copolymers admixed with the former (1).

According to the present invention, (A) from about 0.05 to about 20parts by weight of one or more members of the group of stabilizercopolymers comprised of unsaturated carboxylic acid salt-vinyl monomeris added to (B) each 100 parts by weight of at least one member of thegroup of chlorine-containing polymers as defined in the foregoing (a)through (d). When the stabilized composition comprises less than 0.05part by weight of a stabilizer per 100 parts of the chlorine-containingpolymer, the stabilizing effect of said stabilizer is insuflicient and asatisfactory stabilization of the chlorine-containing polymer cannot beobtained. On the other hand, when the stabilizer copolymer is used in anamount in excess of 20 parts by weight per 100 parts ofchlorine-containing polymer, there does not always result an increase inthe stabilizing effect in proportion to the increase in the amount ofthe stabilizer, but rather the processing property of the composition isdeteriorated due to the high melting point of the stabilizer, per se.Moreover, the use of such large amounts of the stabilizer is undesirablealso from the economic point of view.

The eificiency of the copolymer stabilizer pursuant to the presentinvention may be further enhanced by its combined use with variousadditional compounds as follows.

(a) Conventional stabilizers:

metallic soaps-zinc, cadmium, lead, aluminum, tin and alkaline earthmetal salts of higher fatty acids (such as lauric acid, stearic acid,oleic acid, ricinoleic acid, sebacic acid and their mixed fatty acids).

organic acid sa1tslead, zinc, cadmium, aluminum, tin and alkaline earthmetal salts of organic acids such as nonyl phenol, ethyl acetoacetate,diethylcaproic acid, naphthenic acid and Z-ethylhexylic acid.

organic tin compoundsdibutyl tin dilaurate, dibutyl tin maleate, dioctyltin, dilaurate, dibutyl tin mercaptide and polymer-type organic tincompound.

These conventional stabilizers may be added at the rate of from about0.1 to about 15 parts by weight per 100 parts by weight of thechlorine-containing polymer.

(b) Lubricants for providing the chlorine-containing polymer compositionwith lubricity:

higher fatty acids and metal salts thereof higher aliphatic alcoholshigher aliphatic amides comparatively macromolecular organic polymerssuch as AC polyethylene These lubricants may be added up to about 15parts by weight per 100 parts by weight of the chlorine-containingpolymer.

(0) Plasticizers:

phthalic esters such as dioctyl phthalate (DO'P) fatty acid esters suchas stearic ester straight-chain dibasic acid ester such as dioctyladipate epoxy compound such as epoxidized soybean oil phosphatecompounds such as tricresyl phosphate chlorinated olefin, chlorinatedparaflin, or chlorinated rubber These plasticizers may be employed bycombining one or more of them with the chlorine-containing polymer atthe rate of from about 2 to about 100 parts by weight of the former per100 parts by weight of the latter.

(d) Other additives:

epoxy compoundsmay be added at the rate of 0.1-20

parts by weight per 100 parts by weight of the chlorinecontainingpolymer.

Further, chemical blowing agents, antistatic agents, pigments, dyes,extenders or fillers may also be employed in combination with thestabilizer of the present invention.

A preferred method for making metals of different kinds display theirsynergistic stabilizing effects most efficiently when they are used forthe stabilization of chlorine-com.

tainnig resins, using a stabilizer copolymer comprised of unsaturatedcarboxylate-vinyl monomer according to the present invention, is tocombine at least two metal salts of unsaturated acids deemed to havesynergistic stabilizing effect at the time of the polymerization of saidcopolymer, and to make said metal salts copolymerize with the vinylmonomer. According to this method, there exists-within one and the samemolecule of the obtained copolymeric stabilizer-metals capable ofdisplaying synergistic stabilizing effect and, by virtue of such metalsthe resultant synergistic stabilizing effect is far superior to that ofa stabilizer according to the coprecipitation method. The copolymerscapable of displaying such a synergistic stabilizing etfect, as abovedescribed, include, for instance:

Zn acrylate-Ca acrylate-laurylvinylether copolymer,

Zn acrylate-Cd acrylate-acrylonitrile copolymer,

Cd acrylate-Ba acrylate-methylmethacrylate copolymer, Cd-Ba-Znacrylate-acetylvinylether copolymer,

Zn-Ba acrylate-laurylvinylether copolymer, and Cd-Ba-Pbacrylate-laurylvinylether copolymer.

Although the foregoing examples refer only to acrylates, the sameadvantageous results are achieved with copolymers employingmethacrylates or crotonates, instead of acrylates.

As for the other well-known conventional additives referred to above,they will bring about the same advantageous effects as they do in theprior art procedures, When they are combined with the copolymerstabilizer according to the present invention and added to thechlorinecontaining resin.

Next, it is to be noted that one of the characteristics of thecomposition according to the present invention is its excellenttransparency. That is, the transparency of the chlorine-containing resinper se is scarcely diminished by mixing in the stabilizer copolymeraccording to the present invention. Especially, the copolymerstabilizers, except those copolymer stabilizers which contain the leadsalt, are excellent because they do not substantially reduce thetransparency of chlorine-containing resin; nevertheless, even thecopolymer of the lead salt according to the present invention is farsuperior to, for instance, lead stearate of the prior art as regardstheir effect on transparency.

The following Table 1 lists the comparative values of the transparencyof sheets obtained from compositions prepared by adding conventionalstabilizers to polyvinyl chloride and the transparency of sheetsobtained from compositions prepared by employing the copolymerstabilizers according to the present invention.

Each composition comprised parts by weight of polyvinyl chloride, 2parts by weight of the stabilizer and 0.5 parts by weight of stearicacid. The composition was molded into the form of a sheet (of 1.6 mm.thickness) by roll processing at C. for 10 minutes. The transparency ofthe resultant sheet was determined by measuring the light transmittancyby means of an HEZE Tester.

7 TABLE 1 Stabilizer contained in Percent composition: transmittancyNone Zinc stearate 80.8 Zinc 2-ethyl-hexoate 82.8 Dibutyl tin dilaurate93.9 Cadmium stearate 81.5 Cd Ba complex stabilizer 80.9 Dibutyl tinmaleate 94.9 Zinc acrylate-acrylonitrile copolymer 93.8

Zinc acrylate-laurylvinyl ether copolymer 93.9 Zincacrylate-methylmethacrylate copolymer 92.9 Zinc acrylate-styrenecopolymer 76.3

The values compared in Table 1 are those which were obtained when 2parts by weight of the stabilizer was contained in the respectivecompositions as above described. With regard to the conventionalstabilizers comprising metallic soaps, if the amount thereof usedexceeds 2 parts by weight, the value of the transparency becomes lessthan half that shown in the foregoing Table 1. With regard to thestabilizers according to the present invention, on the other hand, evenif the amount thereof used is increased to about parts by weight, thereduction of transparency is trifling. In light of the foregoing, it isunderstood that the copolymer stabilizer according to the presentinvention is possessed of an efiiciency at least substantially equal tothat of the organic tin compounds which have heretofore been rated asthe best stabilizers from the View point of harmlessness with respect tothe transparency of the polymer.

Further, the stabilizer copolymers of the present invention containingany one of the unsaturated carboxylates of calcium, magnesium, aluminumand zinc are most suitable as a nontoxic stabilizer ofchlorine-containing resin for use as food packaging or water supply pipematerials. These chlorine-containing resin compositions comprising theunsaturated carboxylate copolymers not only display an excellent thermalstabilizing elfect as compared with conventional compositions employingcalcium, aluminum or zinc soaps, but also the eflluence of metals fromthe stabilizer copolymer is extremely small in amount. For example, whena PVC sheet composition produced by employing a conventional zincstearate stabilizer and a PVC sheet composition produced by employing azinc acrylate-laurylvinyl ether copolymer stabilizer, according to thepresent invention, were dipped in pure water, 5 percent Na CO solution,5 percent citric acid solution and 50 percent ethyl alcohol solution,respectively, at a temperature of 80 C. for days, and then the amount ofmetals which flowed out into or became present in the respectivesolutions was calculated, the amount of said metal efiiuent in case ofthe copolymer stabilizers according to the present invention proved tobe only A of that when zinc stearate was used.

Further details of the invention will become apparent from aconsideration of the following preferred embodiments, which are givenfor purposes of illustration only.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 Into a 2 liter resinflask equipped with a reflux condenser and an agitator was introduced 1liter of a 50 percent aqueous solution of ethyl alcohol. Then 210 gr.(2.1 equivalent) of methylmethacrylate and 90 gr. (0.87 equivalent) ofzinc acrylate were mutually dissolved therein. The thus preparedsolution was heated on a water bath and, while being agitatedvigorously, 2 gr. 0f benzoyl peroxide was added thereto.Copolymerization was effected at 75 C., the boiling point of thereaction sys tem. Three hours later, the reaction was discontinued. Thecontents were immediately filtered out and were subjected to washingwith an aqueous alcohol solution several times. After drying with avacuum drier at C. for 8 hours, a copolymer containing no unreactedmonomers was obtained in the form of an extra fine, white powder. Thepolymer yield was 25 percent, the zinc content in the copolymer was 20.0percent, and the ratio of zinc acrylate among the unreacted monomerswithin the reaction solvent was 12.0 percent by equivalent. When thepolymerization was carried out for more than 5 hours by employing asolution of the same composition as referred to above, the resultantcopolymer contained clotform products. Five parts by weight of thepowder-form copolymer, free from clot-form products were added to partsby weight of polyvinyl chloride, and there was further added thereto 50parts by weight of a plasticizer and 0.5 parts by weight of a lubricant.The mixture was subjected to molding at C., whereby there were obtainedcolorless, transparent molded goods of excellent thermal stability andweatherproof property. When this product was compared with the moldedgoods produced by employing other thermal stabilizers such as zincstearate, silica gel coprecipitation silica, calcium stearate, leadstearate and dibutyl tin dilaurate and the molded goods produced byemploying unreacted monomers, the results were as shown in the followingTable 2.

TABLE 2 Trans- Stabilizer employed tion, min. property pareney ToxicityZinc stearato 5 Fairld Opaque--. Nontoxie.

goo Calcium stearate 30 do do Do. Silica gel coprecipitation 40 Good.Trans- Toxic.

silicate. parent. Dibutyl tin dilaurate. 80 Excellent do 0. Leadstearate 135 Best Opaque-.- Do. Zinc aerylate-methyl- 60 do Trans-Nontoxic.

methacrylate copolyparent. mer according to the present invention. Zincacrylate monomer.. 5 Fairlyi do Do.

goo Zinc acrylate-methyl- 5 do do Do.

methacrylate copolymer, containing unreacted zinc acrylate.

Example 2 By employing an apparatus similar to that for Example 1, 155.4gr. (1.5 equivalent) of zinc acrylate and 159 gr. (3 equivaent) ofacrylonitrile were made to mutually dissolve in 1.5 liters of 70 percentmethyl alcohol. The resultant solution was heated on a water bath up toabout 65 C., the boiling point of the reaction system, and, whileagitated vigorously, 8 gr. of polymerization initiator (benzoylperoxide) was added thereto, thereby immediately initiating thepolymerization reaction. The speed of the reaction changed in such a waythat at the beginning it was rapid, next it slowed down gradually and, 5hours later, the rate of increase in polymerization became extremelysmall. After an elapsed time of 5 hours, the polymerization reaction wasdiscontinued and the contents of the apparatus were filtered out, washedwith an aqueous alcohol solution and dried, whereby there was obtained acopolymer in the form of ultra fine, citrine powder (of about 1p. insize) and containing no unreacted monomers. The polymer yield was 82.0percent and the zinc content in the copolymer was 17.9 percent. Theratio of zinc acrylate among the unreacted monomers within the reactionsolvent was 9.4 percent by equivalent.

The foregoing powder-form copolymer, when employed as a component of thestabilizer for vinyl chloride resin (PVC), displayed a superb thermalstability and produced a colorless, transparent composition.

Despite the fact that the zinc acrylate-acronylitrile copolymer is onecontaining zinc, it did not give rise to zinc burning even in case of anoven test at C. for 100 minutes.

The following formulations (A), (B) and (C) are examples of compositionsstabilized by mixing-stabilimersv Examples of compositions: Parts byweight PVC (Geon 130 Ep) 100 DOP 37 Epoxy compounds 3 Zincacrylate-arylonitrile copolymer 2 Stearic acid (H-st) 0.5

PVC (Geon 103 Ep 100 DOP 37 Epoxy compounds 3 Phosphorous chelater 0.2Zinc acrylate-acrylonitrile copolymer 1.2 Calcium stearate -Q. 0.8 H-st0.2

PVC (Geon 103 Ep) 100 DOP 37 Epoxy compounds 3 Zincacrylate-acrylonitrile copolymer 0.2 Cadmium stearate 0.8 Bariumstearate 1.0 H-st 0.5

The copolymer sstabilizer according to the present invention has anexcellent synergistic stabilizing effect and, when employed as a partialsubstitute for cadmium stearate, is capable of providing more excellentstability and transparency than that obtained when cadmium stearatealone is employed.

Example 3 By employing an apparatus similar to that for Example 1, 600gr. of an aqueous solution containing 80 gr. 1 equivalent) of aluminumacrylate and 100 gr. (1 equivalent) of ethyl acrylate were dissolved in800 gr. of methyl alcohol. The water concentration in the solvent (waterplus alcohol) was 39.4 percent by weight. The thus prepared solution washeated on a water bath up to near the boiling point (65 C.) of thereaction system and, by adding thereto 0.5 gr. of ammonium persulfate, 1ml. of hydrogen peroxide solution (35 percent) and 0.5 gr. of sodiumhydrogen sulfite, polymerization 'was initiated.

Three hours later, polymerization was discontinued, and the product wasfiltered out, washed with an aqueous solution of alcohol and was dried,whereby there was obtained a copolymer in the form of a white powderfree from any unreacted aluminum acrylate. The polymer yield was 55percent, and the aluminum content in the copolymer was 6.9 percent. Theratio of unreacted aluminum arcylate within the reaction solvent is 29percent by equivalent.

The foregoing powderform copolymer, when employed as a stabilizer forvinyl chloride resin, is capable of providing a composition of asuperior thermal stability which could not be expected from anyconventional aluminum stearate and the like. As for the aluminumacrylate-ethyl acrylate copolymer, it has the property that, when it isemployed alone, it colors the PVC products during the early stage oftheir processing like calcium or barium soaps, although to a lesserextent. Therefore, it is more eifective to employ it in combination witha zinc-containing copolymer or soaps of zinc stearate, cadmium stearate,etc. as shown in Example 2.

Example of compositions: Parts by weight Vinyl chloride-ethylenecopolymer Dioctyl phthalate 37 Epoxy compounds 3 Aluminum acrylate-ethylacrylate copolymer 1.0 Zinc acrylate-acrylonitrile copolymer 1.0

AC polyethylene 0.1

The foregoing composition was subjected to roll kneading under atemperature of C. and for 10 minutes, thereby producing a sheet.Subsequently, the PVC sheet was exposed in an oven at 170 C. and, evenafter the lapse of 100 minutes. it remained transparent except it wasjust slightly tinged with yellow.

Example 4 By employing an apparatus similar to that for Example 1, 189gr. (1 equivalent) of lead methacrylate and 104 gr. (1 equivalent) ofstyrene were dissolved in ACL (i.e. aqueous solution of mixed alcoholconsisting of 70 weight percent of ethyl alcohol, 20 weight percent ofmethyl alcohol and 10 weight percent of water). The thus preparedsolution was heated to about 74 C. on a water bath and, while agitatedvigorously, 4 gr. of benzoyl peroxide was added thereto, therebyinitiating the polymerization reaction. The yield of copolymer was 50.5percent after 1 hour, 58.2 percent after 2 hours, 62.0 percent after 3hours and 64.2 percent after 5 hours, respectively, and the increase ofyield subsequent thereto became insignificant. Continuation of thepolymerization reaction beyond 5 hours resulted in the formation ofclot-form products and mixing thereof in the powderform copolymer, sothat best results were obtained when said polymerization reaction wasdiscontinued in less than 5 hours. At the end of 5 hours reaction, theratio of lead acrylate among the unreacted monomers in the reactionsolvent is 8.6 percent by equivalent.

When the eifect of employing the present lead methacrylate-styrenecopolymer as the thermal stabilizer for PVC was compared with thatobtained by employing a conventional stabilizer consisting of leadstearate, it was observed that a sheet consisting of PVC compositionemploying lead stearate showed a rapid deterioration when subjected to80 minutes exposure in an oven at C., while the counterpart thereofemploying a copolymer containing lead methacrylate scarcely showeddeterioration even when subjected to 100 minutes exposure in the sametest.

When respect to the amount of lead flowing out from a sheet consistingof the foregoing composition, according to the present invention, whenan object molded therefrom is placed in water or an aqueous solution ofalcohol, weak alkali and weak acid, the flow-out was very much smallerin the case of a sheet employing said copolymer as compared with a sheetemploying lead stearate as the stabilizer. Accordingly, it may be safelysaid that the former is less toxic than the latter. Besides,

there was observed a conspicuous improvement of the weatherproofproperty of the product using the stabilizer according to the presentinvention.

Example 5 By employing an apparatus similar to that for Example 1,monomers of laurylvinyl ether (LVE), calcium acrylate and zinc acrylatewere, mutually dissolved in isopropyl alcohol (IPA) containing 10percent water, and the thus prepared solution was subjected topolymerization at about 80 C. until'the polymerization reactionpractically came to a halt (i.e. for about 6 hours).

The resultant) suspension was immediately filtered, washed with hotalcohol and dried, whereby there was obtained a copolymer in the form ofa white, ultra fine powder.

The compositions of monomers employed, the polymer yields and thecompositions of copolymer obtained are respectively shown in thefollowing Table 3.

TABLE 3 Composition of monomers Percent composition of employed, gr.polymer obtained Laurylvinyl ether-cine Lauryl- Volume PercentLam'ylacrylate-ealclum vinyl Zinc Calcium reaction polymer Zinc Calciumvinyl acrylate-copolymer ether aerylate acrylate solvent yield aerylateacrylate ether LVE-Zn-Ca:

#5020 45 75 so IPA 1,aoom1- 90.0 56.63 21.29 22.10 45 52.5 .5do.-...-..--.. 88.7 39.67 37.40 22.9 45 so do... as. 2s. 4s 54. 9o 21. sso on .410... 17.1 s2. s1 24.34 22.5 on 45 do 77.6 39.44 36.76 23.8 0030 do--- 75.8 27.33 49.41 23.3

Examples wherein the foregoing copolymers are em- 15 TABLE 4 ployed as astabilizer for chlorine-containing resin will G a be described later inExample 11. we;

y weig O a ea 61"!) Example 6 stearate is meter I 20 additionally 'gest,Into an iron autoclave provided with glass lining, con $35 355; Sheet(Mm) zfif fg 2 f; taining 2 liters of 95 percent benzene denaturedindustrial 1 alcohol solution (which contains about percent water)glgfiggg (150) were placed 30 parts by weight of cadmium crotonate and ggg z 10 100 20 parts by weight of barium acrylate. After adding 4Cadmium Colorless; 120 (160) coo gr. of benzoyl peroxide to thesolution, the autoclave 3 was closed. Then, 50 parts by weight ofliquefied vinyl chloride monomer was poured in the autoclave, the tem-As seen in T bl 4 above, the copolymer stabilizer acperature was raisedto 70 C., and the solution was cording to the present invention ispossessed of aconspicpolymerized while being agitated vigorously. After8 hours, the autoclave was opened and there was obtained a copolymer inthe state of a white suspension. The suspended copolymer was filtered,washed with aqueous alcohol solution and dried, and there was recovereda white extra fine powder. 7

In this case, the polymer yield was 32 percent, the cadmium content inthe copolymer was 36 percent and the barium content in the same was 12percent.

This copolymer, when employed as a stabilizer for a chlorine-containingresin, was capable of producing molded goods of excellent transparencyand thermal resistance.

Example 7 Into a mixture comprising 100 parts by weight of vinylchloride resin (T 1050), parts by weight of DOP, 3 parts by weight ofepoxidized soybean oil and 0.5 part by weight of stearic acid; was added2 parts by weight of a copolymer of zinc acrylate and laurylvinyl etherand the mixture was thoroughly blended. The thus blended mixture wasthen subjected to fusion kneading by two-roll machine heated to 160 C.for 5 minutes, thereby producing a sheet of 0.7 mm. in thickness. On theother hand, for the purpose of comparison, by employing 2 parts byweight each of zinc stearate and cadmium stearate, in lieu of theforegoing copolymer, and in the same way as in the foregoing, two sheetsof 0.7 mm. in thickness were prepared. The results of deteriorationtests conducted on the above three kinds of sheets by means of the gearoven method and a weather-o-meter (in this case, WE-II model machinemanufactured by T oyo Rika K.K. was employed) are as shown in Table 4.The figures in said table represent respectively the time from the startof the test until the sheet assumes a blackish-brown color.

uously high stabilizing efi'iciency as compared with zinc stearate andis almost equal to cadmium stearate in said efficiency, while, as fortransparency, it is superior to both stearates.

Example 8 Excepting that vinyl chloride wherein =800 is employed, inlieu of vinyl chloride wherein F=l050 as employed for Example 7, and DOPis omitted, the same way as procedures described in Example 7 werecarried out to thereby prepare three kinds of sheets of 0.7 mm. inthickness each. The results of the deterioration tests conducted onthese sheets .by means of gear oven method are as shown in Table 5. Thefigures in said table represent respectively the time from the start ofthe test until the sheet assumes a blackish-brown color. The text andfigures in parentheses refer to tests in which 0.5 parts by weight of Castearate was additionally employed in the composition.

cloudy (light orange color; slightly cloudy).

Example 9 Two parts by weight of calcium methacrylatc-lauratemethacrylate copolymer was blended with a mixture of parts by Weight ofvinyl chloride resin (F: 1050), 3.7 parts by weight of DOP, 1 part byweight of epoxidized soybean, oil and 0.3 part by Weight of zincstearate, and a sheet is prepared in the same way as in Example 7. Onthe other hand, for the purpose of comparison, another sheet wasprepared in the same way as the foregoing except that calcium stearatewas employed in lieu of said copolymer. Both sheets were subjected todeterioration tests by means of the. gear oven method. The results ofsaid tests are shown in Table 6. The figures in said table representrespectively the time from the start of the test until the sheet assumesa blackish-brown color.

TABLE 6 TABLE 8 Condition e t Gear oven test Condition ofsheet Gear oventest Stablhzer employed after rolling at 170 0. (min) Stabilizeremployed alter rolling at 170 0. (min.)

copolymer Colorless; transparent" fi g ed w t ge Ternary copolymer Veryslightly colored; so (slightly colored). Calcium ea t Slightly a gecolored; 30 s o g Paste-form stabilizer colored; to (light reddish p qC010T)- slightly cloudy. orange color).

NOTE-JIM bracketed P g ill the table indicate the Nora-The bracketedpassagesin the table indicate the state oirespec- :titftggtrespectivesheets 10 minutes after the start of geartivesheets20minutesaiterthestart ofgearoventest.

Example 10 10 Example 12 The following are examples of practicalcompositions Two parts by weight of a wherein the stabilizer copolymeraccording to the present lde copolymer w blenflcd wlth mlxiurefonslstlwof invention demonstrates its excellent efficiency. 100 parts by weightof vlnyl chloride resln (P=1300), 10 parts by weight of a polymer blendconsisting of acrylo- 15 (A) nitrile-butadiene and polyvinyl chloride(in this case, Nippon Geon Hiker-1203 was used), 50 parts by weight ofExamples of compositions: Parts by weight DOP, parts by weight of DBP,15 parts by weight of PVC (straight resin) 100 methyl chloride stearate(in this case, L-20 manufactured DOP 35 by Asahi Denka K.K. was used)and 3 parts by weight of 20 BOA 5 azo-dicarboxylamide. The thus blendedmixture was sub- Organic tin compound 1 jected to 5 minutes kneading bya two-roll machine heated Zn acrylate-acrylonitrile copolymer 1 up to130 C., whereby there was prepared a sheet of 0.5 Cd-Ba stearate 1 mm.thickness. Subsequently, said sheet and a starch- Chelating agent 1coated ground cloth were afiixed together by applying a Ultra-violet rayabsorbent 0.5 pressure of 50 kgL/cm. for 2 minutes with a press heatedColorant (1) up to 120 C., thereby producing an artificial leathersheet. (B) On the other hand, for the purpose of comparison, byemploying zinc stearate and cadmium stearate respectively PVC (Straightr sin) 100 in lieu of the foregoing copolymer, two kinds of sheets areDOP prepared. These two sheets are also processed for afi'ixing Epoxyplasticizer 5 with a ground cloth respectively in the same way a in theCd stabilizer 0.5 foregoing, producing two kinds of artificial leathersheets. Zn acrylatelallryl Vinyl ether COPOIYIHBT 1 The three kinds ofartificial leather sheets thus prepared Ba stabilizer 1 were subjectedto a foamability test by the gear oven 35 l-at r method. The results ofsaid tests are shown in Table 7. Colorant (1) TABLE 7 Post-pressing Gearoven test at 190 0. condition Stabilizer employed of sheet 2 min. afterthe start 4 min. after the start 5 min. after the start Copolymer Notioamed. 2 times the original thickne due to 2.5 times the originalthickness due Excessive foaming is partially obfoaming; white. tofoaming; uniform in cell strucserved; tinged with brown color Zinestearate Slight foaming 2.5 times the original thickness due Fg i s i zi enlarged due to ex- Foam size is further enlarged;

is observed. to foaming; slightly excessive eessive foaming; slightlybrown. yellowish brown.

foaming is observed; white.

Cadmium stearate Not foamed..-.. 2 times the original thickness due tofoaming: whiter than the above two sheets.

Unevenness oi the surface due to Foam size is enlarged and partialexcessive foaming is observed; collapse is observed; slightly As seen inthe foregoing table, the effect of the method employing ametal-containing copolymer according to the present invention is as goodas that of the conventional method employing cadmium stearate, and isnot accompanied by such a defect as poor foam-stabilization property asis the case with zinc stearate.

Example 11 Two parts by weight of a ternary copolymer obtained inExample 5 (LVE-Zn-Ca#3535) was blended with a mixture consisting of 100parts by weight of vinyl acetate copolymer resin (containing 3 percentof vinyl acetate), 40 parts by weight of DOP, 3 parts by weight epoxidesoybean oil and 0.5 part by weight of stearic acid. The thus blendedmixture was subjected to 5 minutes kneading by a two-roll machine heatedup to 160 0., whereby there was prepared a sheet of 0.7 mm. inthickness. On the other hand, for the purpose of comparison, byemploying 2 parts by weight of a paste-form stabilizer consisting offour parts by weight of zinc stearate, three parts by weight of calciumstearate and 3 parts by weight of epoxide soybean in lieu of theforegoing ternary copolymer, another sheet was prepared. The results ofgear oven tests conducted on these two sheets are as shown in thefollowing Table 8. The figures in said table represent respectively thetime from the start of the test until the sheet assumed a blackish-browncolor.

white. brown.

Parts by weight PVC (vinyl acetate copolymer) Plasticizer 40 Calciumcarbonate 350 Asbestos Rosin acid salt 10 Titanium oxide 15 Znacrylate-Ca acrylate-lauryl vinyl ether copolymer 3 Lead stearate 0.5

1 Some quantity.

With reference to the term equivalent as used above in referring to theweight of the salts of unsaturated carboxylic acid in the entire monomercomposition, Zn, Pb, Cd, Ca, Mg, Ba and Al combine with acrylic acid,methacrylic acid or crotonic acid to form salts of the acid, tworepresentative examples of which are indicated at (1) and (2) in thefollowing table. The molecular structure of a representative vinylmonomer is indicated at (3) in the following table.

15 16 TABLE 9 The embodiments of the invention in which an exclu- SMolecular one GQHMP 1ive property or privilege is claimed are defined asfol Moleeularstrueture weighflgr.) lent (g -l a) 0 207 3 103 65 1. Acomposition comprising (A) a chlorine-containu mg polymer selected fromthe group consisting of CH;=OHC (a) polyvinyl chloride (b)polyvinylidene chloride (0) copolymers of a first monomer selected fromthe group consisting of vinyl chloride and vinylidene 1Q chloride, andat least one additional copolymeriza- OHI=CH G ble monomer selected fromthe group consisting of vinylidene chloride, ethylene, propylene,isobutylene,

O acrylonitrile, alkyl vinyl ether Whose alkyl group (Zincacrylate)contains 1 to 18 carbon atoms, vinyl alkyl ester (2) Q 240 80 whosealkyl group contains 1 to 18 carbon atoms, CH acrylic ester wherein thealkyl group of the ester l contains 1 to 18 carbon atoms, methacrylicester 0\ wherein the alkyl group of the ester contains 1 to l O 18carbon atoms, styrene, maleic anhydride, maleic ll ester wherein thealkyl group of the ester contains CH=OH CO AI 20 1 to 18 carbon atomsand vinyl chloride (d) a blend of (1) at least one member of the groupGHFCHJ] of polymers (a), (b) and (c), and (2) at least one memberselected from the group consisting of styrene butadiene copolymers,acrylonitrile butadiene (Aluminum acrylate) oopolymers,acrylonitrile-styrene copolymers, acrylo- 3) OH: 100 100 nitrilebutadiene styrene copolymers, methylmethacrylate-butadiene-styrenecopolymers and ethylene- CH'=CC 000E vinyl acetate copolymers r y acontaining admixed therein, (B) from about 0.05 to about 20 parts byweight, per 100 parts by weight of said chlo- Thus, the term equivalentas used herein is defined as ine-containing polymer, of a powder formcopolyrner follows: stabilizer, in which each molecular chain of thecopolymer consists essentially of the following monomer units: oneeqmvalent (1) at least one metal salt selected from the group molecularwelght of monomer consisting of the zinc, lead, cadmium, calcium,magnumbel 0f Polymerizable double bonds nesium, barium and aluminumsalts of an acid se- Thus, one equivalent of the polymerizable vinylmonomer lected from the g p consisting of acrylic acid, is equal to themolecular weight thereof. One equivalent methacrylic acid and crotonicacid; and of the metal salt of the carboxylic acid depends on the (2) atl ast ne vinyl m nom r Sel cted from the group valence of the metalused. Thus, the term percent by consisting of alkyl acrylate esterswhose alkyl group equivalent as used herein with reference to the ratioof s 1 i0 13 carbon atoms, alkyl methacl'ylate esters metal saltmonomers to the total weight of monomers lWllOSB alkyl group has 1 to 18carbofi atoms, ymeans the ratio of the number of equivalents of metalacrylonitrile, alkyl Vinyl ethfirs alkyl salt monomers divided by thesum of the number of equivgroup has 1 to 18 carbon atoms, vinyl chlorideand alents of salt monomers added to the number of equivvinyl nChloride; alents of polymerizable vinyl o the copolyrner beingsubstantially free of unreacted mon- In some instances the metal saltsof acrylic acid, meth- Omersacrylic acid and crotonic acid are crystalshaving a low 2. A COmPOSi'EIOH according to 3 0 111 Whlch the solubilityin water, in which case water is supplied to 130- Powder p y has a meanPamela SlZe of about lymerization system separate from the crystals.However, o M- the reaction of acrylic acid, methacrylic acid andcrotonic A mp i i n acwrding to claim lIl In the acid with the metal isgenerally carried out in an aqueous p y the Weight ratio 0f Said metalsalt 18 between solution, in which case the reaction product (the metalabout Perfient y equivalent a about 75 Percent f) salt of the carboxylicacid) is obtained in the state of an equivaknnbawd the total Welght 0fthe monomers m aqueous solution. The reaction product obtained in thisthe p y state can be added to the polymerization system, as is, 4. Acomposition according to claim 1, in which the whereby both the metalsalt of the carboxylic acid and al lt is Zin acrylate and Said vinylmonomer is the water are supplied to the polymerization system toalkylvinyl ether whose alkyl group has 1 to 18 carbon gether. Example 3 is anexample of such a procedure. a ms- The gear oven method referred toabove is similar References Cited 10 the method for testing the thermalstability of plas- UNITED STATES PATENTS tics by the use of acirculation air oven according to ASTM D794-49. According to the gearoven method, the gepkms Plastic composition being tested is kneaded at160 C. 3265675 8/1966 Z;$ g 5 R for 10 minutes (in some cases at 170 C.or 180 C. for 10 minutes) by a heated roller and is obtained in the3576782 4/1971 Molbert et 260-899 form of a sheet. The sheet is cut intotest pieces (2 cm. in length x 1.5 cm. in width it about 0.1 cm. inthickness). JOHN BLEUTGE Pnmary Exammer The test pieces are placedinside a circulation air oven ZIEGLER, Assistant Examine! (gear oven),which is maintained at i2 C. (in some cases at C. or 150 C.). The testpieces are removed after given periods of time (usually 20 minutes, butin 260-23 XA, 31.8 M, 45.1 R, 45.75 R, 45.85, 80.71, some cases 30minutes) and observations are made as to 80.76, 80.77, 80.8, 85.5 R,86.3, 87.5 R, 87.5 C, 87.5 G, the deterioration thereof (color andmechanical strength). 75 8 7.7, 88.1 R, 891, 896, 899

